An audio speaker device mounted on a two-wheeled motor vehicle has been conventionally installed in a front cowling of the two-wheeled motor vehicle. Since the front cowling can reduce a wind pressure acting on the speaker device and decrease an influence of the wind pressure on a speaker unit, the audio speaker device of this type has been popular as one that constitutes an audio system for a driver. Such a speaker device has been disclosed in, for example, Japanese Patent Application Laid-open No. 2000-228793 and Japanese Utility Model Laid-open No. S62-52586.
Recently, the regulations have been revised in Japan to permit tandem riding for riding a passenger on a rear seat of a two-wheeled motor vehicle on express highways. Accordingly, there has been a demand for installing a rear seat speaker device near the rear seat that enables a rear seat passenger to enjoy high quality sound.
However, if the speaker device is installed near the rear seat, high wind pressure acts on the speaker device due to lack of a windshield effect differently from installation of the speaker device in the front cowling. Due to this, a diaphragm of the speaker unit is forced inside by the wind pressure to make it difficult to produce sound. Furthermore, if this state continues for a long time, then a voice coil can possibly enter an overheated state and can be destroyed.
Moreover, such a problem occurs not only to the speaker device mounted on the two-wheeled motor vehicle but also any speaker device used in a strong wind.